Both underweight and obese patients are prone to relapse after ablation of paroxysmal atrial fibrillation

Background Being overweight has been associated with arrhythmia recurrence after atrial fibrillation (AF) ablation, but the optimal threshold to identify high risk patients has not been well established. Studies investigating the relationship between underweight and ablation outcome are also limited. This study aimed to investigate the impact of body mass index (BMI) on the recurrence after AF ablation and to determine the optimal cut-off of BMI to identify patients at risk of recurrence. Methods Paroxysmal AF (PAF) patients undergoing primary ablation with pulmonary vein isolation were enrolled. Patients were grouped based on 3 BMI discretization methods: pre-defined BMI category, BMI quartile and optimal equal hazard cut-off. Atrial tachyarrhythmia recurrence at 12-month after ablation was the study endpoint which was compared between groups by using the Kaplan-Meier method. Results Out of 561 patients (mean BMI 25.5 ± 5.1 kg/m2) enrolled, arrhythmia recurrence at 12-month after ablation was found in 29 (43.9 %) of 66 underweight, 39 (21.7 %) of 180 normal weight, 30 (17.4 %) of 172 overweight, and 50 (35.0 %) of 143 obese patients (Log Rank P < 0.001). BMI presented a “U” shape relationship with arrhythmia-free survival. Hazard-based optimal BMI was 20.00 kg/m2 for left cutoff and 29.14 kg/m2 for right cutoff. In multivariable analysis, BMI ≤ 20.00 kg/m2 (HR=2.258, P < 0.001) or > 29.14 kg/m2 (HR=1.702, P = 0.006) was independently associated with arrhythmia recurrence after adjustment of other confounders. Conclusions The relationship between atrial tachyarrhythmia recurrence after PAF ablation and pre-ablation BMI appeared to be U-shaped. Individuals whose BMI was ≤20.00 kg/m2 or >29.14 kg/m2 were at high risk of arrhythmia recurrence.